Subaortic stenosis refers to an obstruction or narrowing at the outlet of the left ventricle just below the aortic valve. In typical subaortic stenosis, the aortic valve itself is normal.
In the normal heart, there are two sides, and each side has a pumping chamber, called a "ventricle". The unoxygenated blood comes back from the body to the right side of the heart, where it collects in the right ventricle. The right ventricle pumps this blood through the pulmonary artery to the lungs, where it collects more oxygen.
The blood, now full of oxygen, returns to the left side of the heart and the left ventricle, where it is pumped through the left ventricle's outflow tract to the aortic valve and out to the body through the aorta. In a heart with subaortic stenosis, it is difficult for the left ventricle to pump the blood out to the body because of this narrowed area in the outflow tract.
Subaortic stenosis causes two main problems for the heart:
- Extra work for the left ventricle to pump blood through the obstruction
- Turbulent blood flow created by the narrowing may damage the aortic valve, causing an otherwise normal valve to leak (called "aortic valve insufficiency")
There are two kinds of subaortic stenosis:
- Discreet subaortic stenosis, the more common form of subaortic stenosis occurs when a membrane made up of fibrous tissue forms the obstruction underneath the aortic valve.
- Tunnel subaortic stenosis, less common and more complex, occurs when the pathway between the ventricle and valve is narrow for the entire distance
Surgery for Subaortic Stenosis
The operation for discreet subaortic stenosis has a high likelihood of success. The operation begins with a vertical incision in the middle of the chest and dividing the breastbone. While repairing this area, it is necessary to work on a still, quiet heart, so use of the heart-lung bypass machine is required. The bypass machine will take the blood returning to the heart from the body and redirect it through a machine that will replace the oxygen in the blood. The blood is then returned to the body on the other side of the heart, allowing the heart to be still while it is repaired.
The subaortic stenosis is fixed by opening the aorta just above the aortic valve. The subaortic membrane can be seen through the valve. The membrane can then be cut out, leaving the left ventricle's outflow tract open and smooth. This operation is called asubaortic resection.
It is uncommon to have major complications after a subaortic resection. It is possible to have a leftover membrane, though it is extremely unusual for that to cause any remaining obstruction. Other very uncommon complications include damage to the aortic valve itself, heart block, which is a problem with the electrical conduction of the heart, or creating a hole between the two pumping chambers (ventricular septal defect). Most patients who undergo a subaortic resection are able to be discharged with 3-4 days after surgery.
It is possible for the subaortic membrane to regrow. There is no good way of predicting regrowth of the membrane from child to child. Thus, patients with subaortic membranes need to be followed for long periods of time by a pediatric cardiologist to make certain that regrowth of the membrane has not occurred.
Note: This page is meant to be a helpful, informative introduction on the subject of Sub-aortic Stenosis. The information may not be applicable to all cases, especially if there are additional defects. It is not meant to replace the opinion of a personal physician.